Packet switched networks are generally (at the data link layer), connectionless, shared bandwidth networks which interconnect nodes in an arbitrary way. In order to establish a connection between the nodes for transmission of data, a routing mechanism is required. Current routing protocols are designed to cope with dynamic and unpredictable volumes of data transfer through networks that are characterized by dynamic topology composed of many nodes that communicate with each other in an arbitrary and random way. These networks are typically enterprise networks or the Internet. To address these problems, routing protocols are adapted to cause each router to continually learn the network topology and continually collect information about traffic status throughout the network, take note of the volume of data being routed through each node, calculate optimized routes for each possible connection and update routing tables at each routing node. Thus, each router computes, independently of the other routers, its own routing table, which is the basis for its forwarding decisions. The information is based on local (adjacent hops) information, as the individual routers have no knowledge of the overall traffic load or performance in the network. Therefore, it is sub-optimal, on one hand, as it does not take into account the other nodes in the network, while heavily burdening the routing node, on the other hand.
U.S. Patent Application 20020150041 to Reinshmidt, et al. describes a method and system for improving the quality of service for transportation of selected data packets over an IP-based data network, such as the Internet. The method utilizes servers in the customer's environment, each of which serves as a source node or destination node. Preferably, for each link, several alternative paths are preselected. The servers contain unique software which allows the servers to exchange test packets between them to monitor and analyze the transportation parameters of each alternative path. When an optimal path is identified, the server modifies the header of the data packet, thereby causing the data packet to be forwarded to the destination node via the selected optimal path(s).
In this method, the paths are monitored between pairs of nodes and not globally. Furthermore, the data is not collected over time, so the routing decision is based only on instantaneous information at any given moment.
U.S. Patent Application 2002/0174246 to Tanay, et al. describes a centralized system that computes routing tables for routers in an IP protocol network, and removes the task of computing routes from the individual routers. This system includes a network traffic statistics gathering system, a matrix formation and optimization system for classifying the traffic into classes and computing optimized routes for every traffic class according to the traffic statistics, and a distribution system for distributing routing tables, including information concerning the optimized routes, to the individual routers. This system, which is limited in use to an IP networking system, must learn the new topology state of the network whenever there is a change of any sort. Since these computations are required continually, the network is burdened with large quantities of computations, and automatically “updates” routing tables, substantially in real time, even if there are no changes, thereby slowing down data transfer in the network as a whole.
It will be appreciated that updating of routing tables or reconfiguration in these Internet-type networks occurs continually, without regard to any specific criteria. Rather, the rate of reconfiguration in networks using these systems is determined by the size and complexity of the network, the quantity of calculations, and the speed of calculation and updating the routing tables by the system.
Carrier transport networks, for example, metro area networks, which are used to transport core data traffic, do not resemble enterprise networks or the global Internet. Rather, the carrier transport network is a conventional telephony network, and is characterized by different attributes:                The logical network's topology is usually mesh based.        The physical network is usually ring based.        The network consists of well-defined autonomous routing domains.        Each node is connected to specific node(s) within each domain.        Available routes are known and limited in number, and are static until the topography of the network changes.        All traffic of one service from one node within each routing domain is destined to a relatively small, finite and constant group of nodes.        
These networks suffer from the disadvantage that they are inefficient. In order to ensure that all required traffic is transported over the network within a reasonable time, the network is often under-utilized. Thus, empty frames are often sent over the network.
Furthermore, it will be appreciated that the complex routing protocols described above, designed for generalized global and dynamic topology networks, which require constant updating of routing tables in accordance with the actual state of the various nodes in the network, are not suitable for establishing routes in the routing domain of a carrier network, such as a metro network. This is because they are too complex, and they are not resource efficient or cost efficient.
Accordingly, there is a long felt need in the art for a routing method and system for metro and sub-networks of carrier networks, and so forth, having the stability and reliability of conventional carrier systems, and it would be desirable to have such a routing system which is as flexible and adaptable as are systems of conventional global networks.